1. Field of the Invention
The present invention relates generally to radiation-based two-dimensional and three-dimensional locating systems and more specifically, to a satellite-based locating system which in one preferred embodiment utilizes at least two spaced satellites in geosynchronous orbit scanning a preselected region on the earth's surface in intersecting simultaneous rotation patterns for precisely locating a point source of energy. Such device can be used to find lost or stolen items or to provide position information for navigation systems. It can also be used to provide location information to trucking and shipping companies, taxicab companies, airlines, bus and train companies, construction companies, surveyors and the like. It can also be used to determine the exact present position of any person or thing on which a suitable transmitter is located. Thus, the present invention can help in finding lost or kidnapped children. It can be used as means for instant communication of auto accidents or road emergencies as well as portable security devices for travelers, hikers, joggers and the like. A passive receiver-calculator version can be used to determine precise local position based upon peak detection of satellite down-link scanned transmissions. As used herein the "peak signal detection" includes other signal direction detection means.
2. Prior Art
The need for a reliable means for quickly and accurately locating the position of an object or person has long been recognized. In emergency situations such as shipwrecks, aircraft crashes or automobile accidents, the ability to quickly and accurately determine location is often a life and death matter. When a child is lost or has been kidnapped, fast and accurate location of his whereabouts is equally a life and death situation. Furthermore, for the elderly or infirm, the means of instantly communicating their exact present location in the event of a medical or other emergency returns to them the freedom to travel and independence. To the dispatcher of a taxicab company, instant knowledge of the exact location of each cab in the fleet allows him the time and cost savings of directing the nearest taxicab in his fleet to respond to a call from a customer. Of course, such time and cost savings can be realized in analogous service industries such as high speed delivery services and the like. A reliable and accurate locating system when used on aircraft offers aircraft collision avoidance as well as superior navigational information allowing straight line flight to any destination thereby saving both time and fuel. Upon approach to an airport, aircraft can utilize the added accuracy of such a navigational capability to provide instrument landing systems at any airport rather than the limited number of airports now offering such capability. The same advantages can be used on ships for allowing lower cost and great flexibility in scheduling due to the time savings of straight line navigation over long distances. In military applications, the exact position of troops and vehicles can prove vital to the battlefield commander. The ebb and flow of the battle can be instantly seen in real time presentations of troop and armament locations. For diplomats in hazardous areas, a precise and portable location system offers a means of security in the event terrorist activity results in taking hostages. The chance for successful rescue is greatly improved by knowing the exact present location of the hostage. Such locating devices may also be advantageously used in security systems such as car alarms.
Prior art attempts to provide fast, accurate location information suffer major limitations including high cost, complexity, inaccuracy, large size and weight and limited operating range. Relevant prior art includes the following U.S. Pat. Nos.:
3,063,048 Lehan et al
3,242,494 Gicca
3,440,635 Hull
3,702,477 Brown
3,703,714 Andrews
3,786,413 Matthews
3,789,409 Easton
3,795,896 Issacs
3,852,750 Klein
3,852,763 Kreutel Jr. et al
3,893,069 Mason
3,906,204 Rigdon et al
3,941,984 Chappell et al
4,012,728 Fowler
4,114,155 Raab
4,161,730 Anderson
4,177,466 Reagan
4,188,614 Habib Jr.
4,260,982 DeBenedictis et al
4,276,553 Schaefer
4,359,733 O'Neill
4,383,242 Sassover et al
4,445,118 Taylor et al
4,523,178 Fulhorst
U.S. Pat. No. 3,063,048 to Lehan et al is directed to a discovery and location system which utilizes a single satellite for determining the position of a vehicle. The transmitter provides for a continuous wave signal to the satellite. However, the satellite is not stationary and as it approaches and recedes, the frequency of the signal received by the satellite changes due to the Doppler effect. When the satellite is closest to the object, the frequency of the received signal decreases at a maximum rate. Within the satellite, a phase-lock loop locks a variable frequency oscillator to the incoming signal. The output of the variable frequency oscillator is then beat against the output of a crystal oscillator to produce an audio beat signal whose frequency varies in a similar manner when taken with respect to the incoming signal.
U.S. Pat. No. 3,440,635 to Hull is directed to a police alarm-type system which provides for a transmitter to be carried on a person. In this reference the inventor uses a portable alarm transmitter carried by the person in order to signal a central location such as a police station by employing direction finders at two of the stations in a simultaneous manner. The capability of determining the origin of the alarm signal from the transmitter is provided and the person sending the signal may be located.
U.S. Pat. No. 3,703,714 to Andrews is directed to a remote alarm system that transmits an alarm signal to a displaced receiver when there is an unauthorized access made into a vehicle. This system includes a portable remote transceiver which transmits and receives signals. There is a vehicle mounted radio transceiver which is both operatively tuned to receive and to transmit to the remote transceiver. The remote transceiver further includes a means whereby a signal may be sent from the transceiver back to the vehicle transceiver to actuate some alarm system on the vehicle if so desired.
U.S. Pat. No. 3,852,750 to Klein is directed to a navigation satellite system. However it uses a plurality of synchronous satellite relays in order to determine the position of various earth bound vehicles. Three synchronous satellites are used alternatively to relay radio frequency carrier amplitude modulated signals with a multiplicity of low frequency tones. Each of the vehicles has a communication receiver including an amplitude modulated detector and a position location system. The amplitude modulated detected output of the communications receiver is coupled to the position location systems and determines the position of the vehicle from the relative phases of the low frequency tones.
U.S. Pat. No. 3,893,069 to Mason discloses a vehicle alarm system for alerting an owner of an unauthorized entry to his vehicle. The system includes a transmitter/receiver which may be in the form of a walkie-talkie unit. The owner of the vehicle may be in the range of the transmitter and is warned when anyone tampers with the vehicle through activation of a plurality of compartments which is what activates the transmitter when any of each of those switches is closed. Thus, this patent discloses the general concept of alerting a vehicle owner or user at a remote location that his vehicle is being tampered with.
U.S. Pat. No. 3,906,204 to Rigdon et al discloses a satellite positioning system to determine the position of any type of vehicle on the earth's surface by processing signals sent from the satellite. However, this is not a stationary satellite and the positioning is based on the Doppler shift in frequencies of the signals sent to the satellite in combination with the orbit description data encoded in the signals.
U.S. Pat. No. 4,177,466 to Reagan discloses an auto theft detection system where there is provided a transmitter adapted to broadcast a call signal through an antenna. An encoder is coupled to the transmitter and modulates the call signal to specify which one of many automobiles the call is directed to. The vehicle may then broadcast a locator signal when queried from a central station. Indicators are provided and are responsive to the location signal to determine the location of the possibly missing vehicle.
U.S. Pat. No. 4,276,553 to Schaefer is directed to a system for determining the position of the radiant energy source from a geostationary, synchronous satellite. The system and method are provided by scanning the beam of a narrow beamwidth antenna in first and second normal directions over a predetermined region which includes the source. The high level of energy transduced by the antenna in each of the scanning directions is detected and correlated with the scanning position of the beam by feeding the output of a detector to a recorder. Despite the fact that the satellite is stationary, it must utilize a plurality of earth stations to hone in on the target.
U.S. Pat. No. 4,445,118 to Taylor et al is directed to a navigation system which utilizes a geostationary satellite in combination with a global positioning system comprising a plurality of satellites. The position coordinates of various vehicles and other sources on the earth's surface is provided by processing a plurality of signals transmitted by the multiplicity of orbiting satellites in the global positioning system. An acquisition aiding signal generated by a control station is relayed to the various user terminals through the geostationary satellite.
The most relevant prior art known to the applicant is U.S. Pat. No. 4,819,053 issued Apr. 4, 1989 which discloses a locating system utilizing a single-point satellite or other such platform cooperating with a single ground station for accurately determining the precise location of a signal source. This patent to Halavais discloses a locating system utilizing a single platform such as a high earth geosynchronous satellite which scans through a combined yaw and roll pattern to generate location information for accurately determining the precise location of a source of radiant energy. Halavais also discloses the use of a single-point satellite-based transmitter having a precisely known antenna scanning pattern to provide local position assessment capability by means of a passive receiver-calculator.